Epoxy resins, in particular those which are prepared from bisphenol A and epichlorohydrin, are known raw materials for preparing high-quality casting resins, coating compositions and adhesives. The aromatic epoxy resins cured by means of polyamines possess, besides good resistance to chemicals and solvents, good adhesion to many substrates. Bisphenol A epoxy resins having as low as possible a viscosity and able to be processed without solvents are, inter alia, of considerable importance for the protection and the renovation of concrete constructions. The curing of the epoxy resins can be carried out using polyamines at ambient temperature. However, the usability of the epoxy resin/polyamine systems is frequently limited by insufficient elasticity or flexibility in the crosslinked state. Durable bridging of cracks requires coating materials which, owing to their high elasticity, "work" over the crack and can in this way absorb high temperature-change stresses by means of high stretchability. In addition, the adhesives sector requires elastic epoxy resin systems which still have sufficient elasticity at low temperatures (e.g., down to -20.degree. C.).
In principle, it is indeed possible to increase the elasticity of epoxy resin systems externally by addition of plasticizers or internally by reducing the crosslinking density. However, external elasticifying agents are not reactive and are not incorporated into the thermoset network. External plasticizers which can be used are tar, phthalic esters, high-boiling alcohols, ketone resins, vinyl polymers and other products which do not react with epoxy resins and amine hardeners. However, this type of modification is limited to only specific fields of application, since it has a series of disadvantages. For example, these additives lead to great disruption of the thermoset structure, have a plasticizing effect limited at low temperatures, tend to sweat out on thermal stressing and ageing, and the cured systems become brittle. For internally increasing the elasticity, additions are made of compounds which react with the epoxy resins or hardeners and are included in the crosslinking. In detail, the elasticizing action is achieved by incorporation of long-chain aliphatic or strongly branched additives into the resin or hardener component. To be able to process the resin/hardener systems without problems, the starting components should have viscosities which are as low as possible.
U.S. Pat. No. 3,538,039 discloses hot-curing mixtures comprising (1) an adduct of a polyepoxide and amine, (2) a polyfunctional anhydride and (3) an accelerator for the anhydride. The adduct is preferably built up from a polyepoxide and aromatic amines such as aniline, m-aminophenol, m-phenylenediamine, and methylenedianiline.
U.S. Pat. No. 3,518,220 discloses hot-curable epoxy resin mixtures comprising (1) an epoxy-group-containing adduct of a polyepoxide containing more than 1.0 vic. epoxy groups and an aromatic amine having at least two active hydrogens on nitrogen and (2) 3-aminopyridine. Amines used are, inter alia, methylenedianiline, aniline, m-aminophenol, and m-phenylenediamine.
DE-A 38 03 508 describes a cold-curing, warm post-crosslinkable resin based on epoxide, obtainable by reaction of a bifunctional epoxide of the formula EQU E--X--E (I)
where
E is in each case a radical having an epoxide function and PA1 X is a divalent organic radical, with a secondary diamine of the formula ##STR1## PA1 R.sup.1 and R.sup.2 can be identical or different and are each hydrocarbon radicals which can be connected to one another to form a ring system, and PA1 Z is a divalent hydrocarbon radical. PA1 A. a polyepoxide; PA1 B. a chain lengthening agent selected from among compounds having the formula 1 or 2; ##STR2## R.sup.6 --NH--R.sup.4 --NH--R.sup.5 2 PA1 C. if desired, a catalyst for the reaction between polyepoxide and chain lengthening agent; and PA1 R.sup.1, R.sup.2 and R.sup.3 are each, independently of one another, hydrogen or a substituent which does not significantly influence the reaction between the primary amines and the epoxide groups and which does not catalyze the reaction of epoxide groups with one another; PA1 R.sup.4 is a C.sub.1-20 alkylene, C.sub.5-20 cycloalkylene, or C.sub.6-20 arylene group, where these groups can, if desired, be substituted by further groups which have no influence; and PA1 R.sup.5 is in each case, independently of one another, a C.sub.3-20 secondary or tertiary alkyl, a C.sub.5-20 cycloalkyl or C.sub.6-20 aryl group, where these groups can, if desired, be substituted by further groups which have no influence; with the proviso that at least one of the groups R.sup.1 or two of the groups R.sup.2 and R.sup.3 must not influence the reaction. PA1 (i) the reaction product of PA1 (ii) a dispersant in a sufficient amount to disperse the composition in water; PA1 (iii) if desired, a solubilizer; and PA1 (iv) water; where PA1 (A) a compound which contains at least two 1,2-epoxide groups and which is the reaction product of PA1 R.sup.1 is an aliphatic, cycloaliphatic, araliphatic or aromatic hydrocarbon radical, each of which may be branched or unbranched, each having from 1 to 30 carbon atoms, each which may be unsubstituted or substituted by one or more of hydroxy, alkoxy, or halogen groups, PA1 R.sup.2 and R.sup.3 are each, independently of one another, PA1 R.sup.4 to R.sup.9 are each, independently of one another, an aliphatic, cycloaliphatic, araliphatic or aromatic hydrocarbon radical, each of which may be branched or unbranched, each having from 1 to 30 carbon atoms, each which may be unsubstituted or substituted by one or more of hydroxy, alkoxy, or halogen groups, and PA1 R.sup.1 and R.sup.2 can form an unsubstituted or substituted cycloaliphatic ring having up to 8 carbon atoms, where R.sub.3 is then a hydrogen atom, the substituents being chosen from lower alkyl (C1-C4), lower alkoxy (C1-C4), halogen, and dialkyl (C1-C4)amino groups, or PA1 R.sup.11 and R.sup.12 are each, independently of one another, hydrogen, a saturated or unsaturated straight-chain, branched or cyclic, with or without heteroatoms in the ring, alkyl having up to 15 carbon atoms, or R.sup.11 and R.sup.12 together can form a cyclic alkylene radical having up to 8 carbon atoms, which is unsubstituted or monosubstituted, disubstituted or trisubstituted by alkyl groups having from 1 to 3 carbon atoms, PA1 R.sup.13 is hydrogen or methyl, PA1 x is an integer from 1 to 100, and PA1 f is 2 or 3, PA1 R.sup.14 to R.sup.17 are independently hydrogen or an alkyl group having from 1 to 8 carbon atoms, and PA1 R.sup.18 is a direct bond, a linear, branched or cyclic, unsubstituted or substituted alkylene group or an arylene or heteroarylene group, the substituents being chosen from lower alkyl (C1-C4), lower alkoxy (C1-C4), halogen, and dialkyl (C1-C4)amino groups, PA1 (B) optionally one or more of 1,2-epoxide compounds which is different from that of (A1) or is the unreacted proportions of the compounds (A1) from the preparation of the compounds (A), PA1 (C) one or more hardeners, and PA1 (D) optionally, further additives.
where
The epoxy resin used is preferably the diglycidyl ether of bisphenol A and the dialkylalkylenediamines used are preferably, for example, N,N'-dimethylethylenediamine and N,N'-diethylethylenediamine. This epoxy resin is used as an adhesive, for coatings and also as matrix composition.
EP-A 496,163 describes a cured epoxy resin containing the reaction product of:
D. if desired, a dihydroxy hydrocarbon compound which can also contain halogen substituents;
where
These chain-lengthened solid epoxy resins are used, inter alia, for powder coating. They have relatively high softening points and relatively high melting points at a lower epoxide equivalent weight compared with the conventionally lengthened epoxy resins. "Epoxide equivalent weight" is the molecular weight of the compound concerned based on the number of epoxide groups ("EV").
One embodiment of EP-A 496,163 relates to the aqueous dispersions of amine-lengthened epoxide resins comprising
A. a polyepoxide; PA2 B. a chain lengthening agent corresponding to one of the formulae 1, 2 (see above) and 17; EQU R.sup.11 --NH.sub.2 17 PA2 C. if desired, a catalyst for the reaction between polyepoxide and chain lengthening agent and PA2 D. if desired, a dihydroxy hydrocarbon compound which can also contain halogen substituents; PA2 (A1) one or more compounds containing at least two 1,2-epoxide groups, optionally in admixture with one or more monoepoxides, and PA2 (A2) one or more amines selected from PA2 hydrogen or one of the radicals specified under R.sup.1, with the proviso that the amino group (NH.sub.2) is not directly bonded to an aromatic and, in the case of R.sup.2 and R.sup.3 being hydrogen, the remaining radical R.sup.1 is one of the following substituents ##STR5## PA2 wherein the R.sup.11, R.sup.12, and R.sup.13 groups can vary in the repeating units; or
R.sup.11 is a linear or branched, unsubstituted or hydroxy-substituted C.sub.4-20 alkyl group.
Besides the above-mentioned amines 1 and 2 as component B, for the epoxy resin dispersed in water use is additionally made in the component (i) B of compounds of the formula (17) R.sup.11 --NH.sub.2. No more details about the type of any branching of the radical R.sup.11 are given in the patent. Chain lengthening agents used are n-hexylamine in Example 8 and n-octylamine in Example 12.
The aqueous embodiment of EP-A 496,163 concerns complex mixtures in which solid resins are supposed to be prepared as stable dispersions in water. Applications given for these dispersions are, inter alia, coatings for ambient temperature curing, in paper latex, in cement dispersions and in other water-containing coatings.
U.S. Pat. No. 4,886,867 describes, inter alia, a method for preparing difunctional epoxy resins of the formula ##STR3##
where R is derived from a bisphenol A diglycidyl ether radical and x=2 to about 10, by reaction of excess epoxy resin with a secondary isopropylamine derivative of a primary polyoxyalkylenediamine or polyoxyalkylenetriamine in the presence of acetone (iPr=iso-propyl radical).
The reaction of the amine component with the bisphenol A epoxy resin is critical. To prevent gel formation, a solvent has to be added in the preparation of the adduct. Suitable solvents are ketones and alcohols, particularly preferably acetone. The difunctional epoxy resins can, depending on the starting material, be solid or liquid and in the cured state give a transparent, flexible, rubber-like material. The examples show that the diepoxides based on bisphenol A resin (Epon.RTM. 828) are semi-solid products and those based on Eponex.RTM. 151 (hydrogenated Epon.RTM. 828) are indeed liquid but have very high viscosities (cf. Table I p. 9/10).
According to U.S. Pat. No. 4,316,003, there is obtained an adduct for curing epoxy resins, particularly for aqueous systems, by first reacting, in a first step, excess epoxy resin with a primary monoamine and then reacting the epoxide obtained in a second step with an excess of a polyfunctional amine. The products of the first step are prepared in the presence of solvents and are directly processed in the second step to give the amine hardener. No statements are made about the storage stability and about possible use of step 1.